1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to the improvement of a single-in-line (SIL) type package for a Hall sensor.
2. Description of the Related Art
A Hall sensor functions to convert variation in a magnetic field into an electrical signal by use of the Hall effect, and is adapted to detect the position of a motor.
FIG. 1A is a front view of the conventional Hall sensor and FIG. 1B is a side view thereof. The conventional Hall sensor shown in FIG. 1 includes pellet 10 which is fixed to Hall sensor bonding plate 11 by soldering, and which is connected to lead terminals 9 and 9' to be connected with external devices. Lead terminal 9' extends from Hall sensor bonding plate 11, and lead terminals 9 are each connected to a corresponding terminal electrode section (not shown) formed on pellet 10 via extremely thin wire 30 of, for example, gold or aluminum by a wire bonding method. The pellet and the extremely thin wire are sealed in package 7 of thermosetting mould resin such as epoxy resin, and thus protected from the exterior. Package 7 projects residual resin portion 16 from the center of edge portion 29. Edge portion 29 is an intersection between end face 28 opposite to end face 27 from which lead terminals 9 are drawn out and surface 31 disposed on the side of Hall sensor bonding plate 11. Residual resin portion 16 will be inevitably formed in a position corresponding to the gate position of a die (not shown) caused by setting sensor bonding plate 11 and the extremely thin wire into the die and then injecting resin into the die from the gate position of the die to form mould resin package 7. The residual resin portion can be removed after formation of the package. However, it is troublesome to remove the residual resin portion, making the manufacturing cost high. Further, it is difficult to completely remove the residual resin portion.
FIG. 2 shows an example of a positional relation between the Hall sensor and a motor whose position is detected by the Hall sensor. In FIG. 2, the left half portion of the brushless motor and the Hall sensor disposed near the brushless motor are shown. Further, in FIG. 2, stator core 26 on which coil 25 is wound is fixed on supporting member 24, and rotor 21 is disposed to surround stator core 26. Magnetic ferrite core 20 is fixed on the end portion of rotor 21. With this construction, rotor 21 may be rotated by supplying a current to coil 25 and thus the motor is driven. Hall sensor 23 is attached to printed board 22 and is disposed near the motor. In the assembling operation, Hall sensor 23 is first fixed on printed board 22, and then stator core 26 is placed on supporting member 24 above Hall sensor 23 and fixed thereon by screws or the like. Further, rotor 21 is disposed over stator core 26. In general, the Hall sensor used to detect the rotation position of the motor is arranged near the coil of the motor in order to enhance the sensitivity of the Hall sensor. The coil of the assembled motor may not be uniformly wound and the right and left portions of the coil tend to be differently wound with respect to stator core 26. Therefore, the mounting position of coil 25 with respect to stator core 26 cannot be uniformly set, and consequently package 7 of Hall sensor 23 to be arranged near coil 25 may be easily brought into contact with, coil 25. In the conventional Hall sensor, residual portion 16 of end face 28 of moulded resin package 7 which lies on the side of pellet 10 is formed to have a sharp edge For this reason, if end portion 17 of package 7 comes into contact with coil 25, the coil will be damaged and may be cut off in the worst case.
In general, the Hall sensor is used with surface 32 on the side of pellet 10 of the Hall sensor facing the motor coil, but it is sometimes used with surface 31 on the side of Hall sensor bonding plate 11 facing the motor coil. In the latter case, residual resin portion 16 projecting from that edge of package 7 lies near the coil. For this reason, the Hall sensor disposed near the motor coil may more easily come into contact with the motor coil so as to cut off the motor coil. Secure prevention against the cut-off of the coil does not permit Hall sensor 10 and coil 23 to position sufficiently close to each other because of the presence of residual resin portion 16.
As described above, it is necessary to place the Hall sensor sufficiently close to the motor coil in order to enhance the sensitivity thereof. However, in the conventional Hall sensor, the edge portion of surface 31 or 32 may come into contact with the coil to cut off the coil in a case where either one of surfaces 31 and 32 is positioned to face the motor coil.